RFID electronic tags are produced by passive contactless integrated circuits, or transponders, which can be of the electrical coupling-type or the inductive coupling-type.
Electrical coupling contactless integrated circuits, or UHF contactless integrated circuits, are electrically powered by a UHF electric field oscillating at several hundred MHz. They send data by modulating the reflection rate of their antenna circuit (a technique called backscattering). Such integrated circuits are, for example, described by the industrial specification EPCTM-GEN2 (Radio-Frequency Identity Protocols Class-1 Generation-2—UHF RFID Protocol for Communications at 860 MHz-960 MHz), which is in the process of being standardized. They are generally used in so-called long range applications, in which the distance between the integrated circuit and a data send/receive station sending the electric field, commonly called a reader, can reach several meters.
Inductive coupling contactless integrated circuits, or RF contactless integrated circuits, send data by load modulation and are powered by inductive coupling in the presence of a magnetic field. The frequency of which is generally on the order of approximately ten MHz. Such integrated circuits are, for example, described by standards ISO/IEC 14443A/B, ISO/IEC 15693 that provide for a working frequency of 13.56 MHz.
FIG. 1 schematically represents a UHF-type electronic tag TG1. The electronic tag TG1 comprises a substrate 10, a UHF dipole antenna 11 comprising two antenna wires 11-1, 11-2, and a UHF integrated circuit 12 having two contact pads connected to the antenna wires 11-1, 11-2.
FIG. 2 schematically represents an RF-type electronic tag TG2. The electronic tag TG2 comprises a substrate 20, an antenna 21 in the form of a coil comprising two windings for example, and an RF integrated circuit 22 having two contact pads connected to the ends 21-1, 21-2 of the antenna coil.
The substrate 10, 20 can be a simple, flexible plastic foil (polyamide, polyester, etc.) having a self-adhesive back face, or even a simple paper substrate. The UHF dipole antenna 11 or the RF antenna coil 21 can be produced by etching a metal layer, by sticking a leadframe onto the medium, and by depositing a conductive ink (screen printing or inkjet), etc. The antenna 11 or 21 is also known to be produced directly on the product by depositing conductive ink on one side of the product, which forms the substrate of the tag.
UHF and RF electronic tags are currently used to identify and/or authenticate the products onto which they have been affixed. The contactless integrated circuit generally comprises an electrically erasable and programmable memory enabling, in addition to identification data, application data, trade data, tracing data, etc. to be saved. Numerous applications are therefore possible including product authentication (prevention of forgery or smuggling), inventory management, supply chain management (product tracking during transit), etc.
Due to the increasingly low cost of contactless integrated circuits, electronic tags will be affixed onto an increasingly significant number of products. To comply with consumer privacy requirements, it has been suggested to produce an electronic tag which can be destroyed by the buyer after purchasing the product. Since an electronic tag is generally read-accessible and write-accessible, it could indeed be used fraudulently to identify or secretly track not only the product bearing the tag but also the person having purchased the product.
Rather than taking the tag out of service by the classic KILL command which is difficult for the end user to check, physical destruction of the antenna circuit is regarded as the most reassuring approach for the consumer. The latter allows the end user to visually satisfy himself that the tag is destroyed.
The document titled “Disabling RFID Tags with visible confirmation—Clipped tags are silenced” by Gunter Karjoth (IBM Zurich Research Laboratory Ruschlikon) and Paul Moskowitz (IBM T. J. Watson Research Center Hawthorne), dated Aug. 31, 2005, Computer Science (RC23710(WO508-164)), describes various approaches for enabling the user to disable an electronic tag, such as:
1) producing all or part of the antenna on a scratch-off material, which is scratched by the user to destroy the antenna,
2) producing all or part of the antenna on a pre-cut medium, which is removed by the user with a grab tab being provided for this purpose, and
3) producing all or part of the antenna on a peel-off layer that the user also removes to disable the antenna, again by using a grab tab.
These various approaches aimed at destroying the antenna do, however, make the structure of the ready-to-fit electronic tags more complex and also increase their cost as a result.
Furthermore, U.S. Pat. No. 6,574,166 describes a method enabling the consumption of tablets arranged in a blister-type packaging to be detected and managed. According to the embodiment represented in FIG. 2 of the patent, a network of electrical conductors (108, 210) is provided in the packaging foil of the blister (foil covering the cells of the blister). The network of conductors is sandwiched between two electrically insulating plastic foils (208, 212) over which an aluminum film (104) extends. The two plastic foils and the aluminum foil form the packaging foil. When the user opens a cell of the blister to eject a tablet, he snaps one of the conductors. The snapping is detected as an open circuit by an electronic circuit connected to the network of conductors.
Similarly, the company ABR Pharma markets a so-called intelligent Med-ic® blister (www.abrpharma.com/PDF/blister.pdf), comprising a grid network of conductors produced by depositing silver- and graphite-based conductive inks on a paper substrate. The network of conductors is stuck onto the aluminum front face of the blister and is formed such that one of the conductors is destroyed when the patient extracts a tablet from a cell. The snapping of the conductor is detected by a 13.56 MHz RFID integrated circuit that retransmits the cell opening data to a reader.
This technique for detecting the consumption of tablets is based on the destruction of conductors incorporated into the packaging foil of the blister, but is not destructive for the antenna circuit since the RFID integrated circuit linked to the network of conductors continues to exchange data with a reader to send information about the number of tablets remaining in the blister.